Leak barriers are typically the second product installed on a residential roofing system. They are a requirement by Alberta building code, and common practice amongst nearly every professional contractor. The purpose of a leak barrier is to provide extra protection around areas of particularly higher concentrations of moisture accumulation. Moisture collects in areas such as valleys and eaves troughs where moisture enters due to ice damming and wind driven rain.
Most leak barriers are of a ‘peel and stick’ assortment, meaning there is a protective film installed on one side which is removed while the product is being installed, which exposes the sticky side beneath. Once the sticky side makes contact with the roof deck, it bonds together to create a firm moisture entry prevention surface.
Along eaves trough areas there is a phenomenon which occurs in colder climates such as Calgary, and Canada in general, which is referred to as ‘ice damming’. Ice damming is exactly as it sounds. It’s when ice builds up and forms a dam which prevents proper moisture run off from the roof top. In essence, heat from your house rises into your attic which warms your roof deck from the inside out. This results in the snow accumulation on asphalt shingles to melt and turn into water which is pulled by gravity towards the ground below. A typical eaves trough system though overhangs your house by a couple linear feet. By overhanging your house, the eaves trough are is not located over a heated area, meaning that snow does not melt as fast as other areas. Water from the melted snow above ends up freezing as it reaches these non-heated overhang areas and turns into ice. The longer and more prolonged this occurs for, the more ice builds up. When ice has built up sufficiently it creates a dam and can become a blockage point for water running off the roof deck above.
In the most extreme circumstances, water begins to pool and flow backwards up under shingles, penetrating the roof system and reaching the roof deck. And this is where your leak barrier shines and proves is worth. It’s firm bond to your roof deck prevents this back flowing water and ice from reaching the wood on your roof deck and your house remains dry.
Leak barriers are typically installed on top of the drip edge, along the eaves trough areas, underneath rake edge, and along the centres of valleys from the top to the bottom.
A typical coverage area for a leak barrier is 36 inches (3 feet) up from eaves trough ends and 18 inches (1.5 feet) on either side of a valley centre. This being said, Alberta Building Code requires that leak barriers cover 12 inches (1 foot) on top all heated areas, this often ends up being farther back than 36 inches from the eaves line. For this reason it is common to see roofers install a 44 inch width roll or even use two rows of 36 inch to provide a total coverage area of 70 inches.
The Alberta Roofing Contractors Association Good Roofing Practices requires leak barriers to be 70 inches of coverage in total.
Choosing an appropriate leak barrier and installing it properly is an important step in every roof system. Speak with a Roof Hospital representative to learn more about leak barriers, how to choose the right one, and how to choose a professional roofing contractor to install it.